NO334219B1 - Power management protocol for a highly variable data rate reverse connection in a wireless communication system - Google Patents

Abstract

A subscriber unit receives a control message, wherein the control message includes an indication of periodic time intervals and an indication of a phase, and wherein each of the periodic time intervals include at least one time slot. The subscriber unit further receives power commands. The subscriber unit transmits signals in the indicated periodic time intervals, wherein each of the transmitted signals is derived from a sequence having the indicated phase and having a transmission power level derived from the received power commands, and wherein the transmitted signals are not transmitted simultaneously with traffic data by the subscriber unit. The subscriber unit transmits traffic data signals, wherein the traffic data signals have a transmission power level also derived from the received power commands.

Description

The increasing use of wireless telephones and personal computers has led to a corresponding need for advanced telecommunications services that were previously thought to be intended only for use in specialized applications. In the 1980s, wireless voice communication became available to a wide audience through the cellular telephone network. Such services were first usually considered to be the exclusive domain of the businessman, because expected high subscription costs. The same was also the case for access to remotely distributed computer networks. Until very recently, only business people and large institutions could afford the necessary computers and access line equipment. As a result of the widespread availability of both techniques, the general population now increasingly wants not only to gain access to networks such as the Internet and private intranets, but also to access such networks wirelessly. This particularly concerns the users of portable computers, "laptop computers", hand-held personal digital "assistants" and the like, who would prefer to access such networks without being tethered to a telephone line.

There is still no widely available and satisfactory solution for providing cheap high-speed access to the Internet, private intranets and other networks that use the existing, cell-shared, wireless infrastructure. This situation is most likely the result of several unfortunate circumstances. For one thing, the usual way of providing high-speed data service in a business environment over a wired network does not easily adapt to the voice-quality service available in most homes or offices. Nor can such standard high-speed data services be easily used for efficient transmission over cell-shared, wireless handsets of the standard type. Moreover, the existing cellular network was originally designed only to provide voice service. As a result, the main emphasis of current digital wireless communication plans is on voice, although certain plans, such as IS-95B, actually provide some degree of asymmetric behavior for to be able to record data transmission. The data rate on a forward traffic channel for IS-95B can e.g. adjusted in increments from 1.2 kbps up to 0.6 kbps for so-called "Rate Set 1", and in increments from 1.8 kbps up to 14.4 kbps for "Rate Set 2". On the reverse connection's traffic channel, however, the data rate is fixed at 4.8 kbps.

Existing systems therefore typically provide a radio channel that can accommodate maximum data rates only in the region of 14.4 kilobits per second (kbps) at best, in the forward direction. A channel with such a low data rate does not lend itself directly to the transmission of data at speeds of 28.8 or even more. 56.6 kbps, which is now commonly available using cheap cable modems, not to mention even higher speeds, such as 128 kbps, which are available with ISDN (Integrated Services Digital Network) type equipment . Data speeds at such levels are quickly becoming the lowest acceptable speeds for such activities as reading (browsing) websites. Other types of computer networks that use higher-speed building blocks, such as the xDSL (Digital Subscriber Line) service, are now also being adopted in the US.

Although such networks were known when the cellular systems were originally adopted, there is mostly no possibility of providing higher speed data services over the cellular network topologies. In wireless environments, access to the channels is unfortunately expensive for many subscribers, and there is competition for them. Whether multiple access is provided using traditional FDMA (Frequency Division Multiple Access), which uses analog modulation on a group of radio carriers, or using newer digital modulation plans that allow the sharing of a radio carrier using TDMA (Time Division Multiple Access, time-division multiple access) or CDMA (Code Division Multiple Access), the nature of the radio spectrum is that it is a medium that is expected to be shared. This is completely different from the traditional environment for data transmission, where the bandwidth of the cables is relatively large, and therefore not usually intended to be shared between several people.

Multi-access plans of the CDMA type are generally considered, in theory, to provide the most efficient use of the radio spectrum. However, CDMA systems only work well when the power levels of individual transmissions are carefully controlled. Current CDMA wireless systems, such as IS-95B, employ two different types of power control in the uplink direction to ensure that a signal from a given subscriber unit arriving at the base station does not destructively interfere with the signals arriving from other subscriber units. In a first process referred to as "open loop power control", a rough estimate of the correct power control level is created using the mobile subscriber unit itself. After a call is established, and as the mobile phone moves around a cell, in particular the path loss between the subscriber unit and the base station will continue to change. The mobile phone continues to monitor the reception power, and to adjust its transmit power. In particular, the mobile unit measures a power level of the forward link signal as received from the base station, and it then adjusts its reverse link power accordingly. If, for example, the reception power level is relatively weak, the mobile unit then assumes that it is relatively far from the base station, and it increases its power level. The reverse is also the case, in that a signal received with a relatively high level indicates that the mobile unit is relatively close to the base station, and it should therefore transmit with reduced power.

However, since the forward and reverse links are at different frequencies, open-loop power control is inadequate and too slow to compensate for rapid Rayleigh fading. Since Rayleigh fading is frequency dependent, m.a.o. open-loop power control alone cannot fully compensate for Rayleigh fading in CDMA systems.

As a result of this, power control with a closed loop is also used to compensate for power fluctuations. As soon as the mobile device gains access to a traffic channel and begins to communicate with the base station, the base station, in the closed-loop process, constantly monitors the level of received power on the reverse link. If the connection quality begins to deteriorate, the base station sends a command to the mobile unit via the forward link to increase its power level. If the link quality indicates excessive power on the reverse link, the base station orders the mobile unit to lower the power.

In the IS-95B standard, the base station sends such power control commands to the mobile unit using a specially coded message sent on a traffic channel on the forward link. These embedded messages contain power control commands in the form of so-called power control bits (power control bits, PCBs). The degree of power increase and power decrease for each bit is nominally specified as +1dB and -1dB. The mobile unit's response to these power control bits is typically expected to be very fast, to compensate for rapid Rayleigh fading. For this reason, these bits are sent directly over the traffic channel. In particular, certain selected bits from the baseband stream are introduced or "punctured" into the traffic stream to provide a separate subchannel for power control at a rate of 800 bits per second. The mobile device thus continuously receives power control bits every 1.25 ms, via such bit puncturing.

Certain optimizations of CDMA systems for data transmission have recently been developed. These systems use certain phase-coded channel allocation plans, which remove phase-coded channels when they are not in use, and then reallocate them to provide more efficient use of the radio spectrum. Ideally, phase-coded channels can be assigned as quickly as possible to different connections, while minimizing the radio frequency signaling required. However, a virtual connection must be kept open between each mobile unit and the base station, whether a phase-coded channel is in use or not. Otherwise, it is necessary e.g. to achieve synchronization again, each time a channel is assigned to or taken away from a particular connection.

Especially for the case of trying to implement signaling with power control with a closed loop, there is unfortunately no active traffic channel into which power control bits can be embedded every 1.25 milliseconds. This would be inconvenient to have to re-acquire the correct power level each time a new code phase channel was assigned.

It is therefore desirable to maintain the correct power level on the reverse connection, also when code phase channels are de-allocated from a particular connection.

US5056109A relates to a method and an apparatus for controlling transmission power in a CDMA mobile telephone system.

In a first aspect, the invention provides a method for use in a base station to provide power control over dynamically assigned return link channels as set forth in claim 1.

In another aspect, the invention provides a code division multiple access (CDMA) base station as set forth in claim 13.

In a third aspect, the invention provides a code division multiple access (CDMA) user device as set forth in claim 25.

In a fourth aspect, the invention provides a method for use in a code division multiple access (CDMA) user device, to provide power control over dynamically assigned return link channels as stated in claim 37.

Preferred embodiments of the invention are indicated in the independent claims.

The present invention is a technique for implementing a code-shared multi-access system which assigns coded traffic channels dynamically on an as-needed basis. This technique maintains a known transmit power level for the reverse link channel equipment, even when the subscriber unit has entered standby mode where no traffic channels are active.

This is achieved in standby mode by causing the base station to measure certain quality parameters for a maintenance heartbeat signal that is sent periodically on a reverse channel from a subscriber unit when it is in standby mode. The heartbeat signal is a minimum signal sent at a rate just sufficient to maintain code phase locking between the subscriber unit and the base station. The speed at which the heartbeat signals are sent depends on the expected maximum speed of physical movement of the subscriber unit. In systems that are expected to support mobility of the type at walking speed, the heartbeat signal needs e.g. only to be sent every few seconds.

The connection quality parameters are preferably a measurement of bit error frequency, but can also be a measurement of noise level, or a measurement of signal power level.

The link quality information is then sent from the base station to the subscriber unit, usually formatted as a link quality report message. The link quality reports are sent on a forward call channel or synchronization channel to a subscriber unit that is in standby mode.

The subscriber unit then uses the link quality information as a parameter for a decision logic circuit or function that ultimately determines the transmit power level for the associated reverse link.

The aforementioned and other aims, features and advantages of the invention will be apparent from the following, more particular description of preferred embodiments of the invention, as illustrated in the attached drawings, where the same reference signs refer to the same parts in the different figures. Fig. 1 is a block diagram of a wireless communication system that makes use of a bandwidth management system according to the invention. Fig. 2 is a diagram showing how subchannels are assigned within a given radio frequency channel for a forward connection. Fig. 3 is a diagram showing how subchannels are assigned within a given RF channel with a reverse connection. Fig. 4 is a state diagram for a connection quality notification system according to the invention.

As we now look more closely at the drawings, fig. 1 is a block diagram of a system 100 for providing high speed data and voice service over a wireless link by "seamlessly" integrating a digital data protocol, such as ISDN, with a digitally modulated wireless service, such as CDMA.

The system 100 consists of two different types of components, including subscriber units 101-1, 101-2 ..., 101-u (collectively the subscriber or mobile units 101) and one or more base stations 170. The subscriber units 101 and the base stations 170 cooperate to providing the functions necessary to provide wireless data services to a portable computing device 110, such as a "laptop" computer, portable computer, personal digital "assistant" (PDA), etc. The base station 170 also cooperates with the subscriber units 101 to allow the transmission of data between the subscriber unit and the public telephone network (PSTN) 180.

More specifically, data and/or voice services are also provided using the subscriber unit 101 for the laptop 110, as well as one or more other devices such as telephones 112-1, 112-2 (collectively referred to here as telephones 112). The telephones 112 can themselves in turn be connected to other modems and computers that are not shown in fig. 1.1 common parlance when it comes to ISDN, the laptop 110 and the telephones 112 are referred to as terminal equipment

(TE, Terminal Equipment). The subscriber unit 101 provides the functions referred to as NT-1 (Network Termination Type 1, network termination of type 1). The illustrated subscriber unit 101 is specifically intended to operate with an ISDN connection of the so-called "Basic Rate Interface" (BRI) type, which provides two bearer channels (B-channels) and a single data channel (D- channel), with the common designation "2B+D".

The subscriber unit 101 itself consists of an ISDN modem 120, a device which is referred to here as a protocol converter 130 which performs the various functions according to the invention, including spoofing 132 and bandwidth management (BW-mgt) 134, a CDMA transceiver 140 and a subscriber unit antenna 150. The various components of the subscriber unit 101 can be realized with discrete devices, or as an integrated unit. E.g. an existing, common ISDN modem 120, readily available from a number of manufacturers, can be used together with existing CDMA transceivers 140.1 In this case, the special functions are provided completely by the protocol converter 130, which can be sold as a separate device. Alternatively, the ISDN modem 120, protocol converter 130 and CDMA transceiver 140 may be integrated as a complete unit and sold as a single subscriber unit device 101. Other types of interface connections such as Ethernet or PCMCIA may be used to connect the computer device with the protocol converter 130.

The ISDN modem 120 converts data and voice signals between the terminal equipment 110 and 112 into a format required by the "U" interface for standard ISDN. The U-interface is a reference point in ISDN systems, which denotes a point for the connection between the network termination (NT) and the telephone company.

The protocol converter 130 performs "spoofing" 132 and basic functions of bandwidth management 134. In general, spooching 132 consists of ensuring that the subscriber unit 101 is visible to the terminal equipment 110, 112 connected to the public telephone network 180 on the other side of the base station 170, throughout the time. The bandwidth management function 134 is responsible for allocating and de-allocating CDMA radio channels 160, including managing the total bandwidth allocated to a given session by dynamically allocating subsets of the CDMA radio channels 160 in a manner also described more complete below.

The CDMA transceiver 140 accepts the data from the protocol converter 130, and reformats this data in the appropriate form for transmission through a subscriber unit antenna 150 over the CDMA radio link 160-1. The CDMA transceiver 140 may operate over only a single radio frequency channel of 1.2288 MHz, or alternatively, in a preferred embodiment, it may be tunable over multiple such channels.

CDMA signal transmissions are then received and processed by the base station equipment 170. The base station equipment 170 usually consists of multi-channel antennas 171, several CDMA transceivers 172 and a function 174 for bandwidth management (bandwidth management, BW-mgt). The bandwidth manager 174 controls the allocation of CDMA radio channels 160 and subchannels, in a manner analogous to the subscriber unit 101. The base station 170 then couples the demodulated radio signals to the public switched telephone network (PSTN) 180 in a manner well known in the art. E.g. base station 170 may communicate with PSTN 180 over any number of different efficient communications protocols, such as primary rate ISDN, or other LAPD based protocols such as IS-634 or V5.2.

To then continue briefly with reference to fig. 1, the bandwidth management 134 and 174 therefore involves causing the CDMA transmitter/receiver 140 to loop back data bits over the ISDN communication path, in order to fool (spoof) the terminal board 110, 112 into thinking that a sufficiently wide wireless communication link 160 the time is available. However, it is only when data is actually present from the terminal equipment of the wireless transceiver 140 that wireless bandwidth is allocated. Therefore, a network layer connection does not need to allocate the assigned wireless bandwidth throughout the communication session. That is, when data is not presented on the terminal equipment to the network equipment, the bandwidth management function 134 de-allocates the initially allocated radio channel bandwidth 160 and makes it available to another transceiver and another subscriber unit 101.

It is also understood that data signals travel in two directions over the CDMA radio channels 160. M.a.o. data signals received from the PSTN 180 are connected to the portable computer 110 in the so-called forward link direction, and data signals originating in the portable computer 110 are connected to the PSTN 180 in the so-called reverse link direction. The present invention particularly involves the way in which a power control mechanism is implemented for the reverse link channels.

In order to better understand how the bandwidth management 134 and 174 achieves the dynamic allocation of radio channels, reference should now be made to fig. 2. This figure illustrates a possible frequency plan for the wireless forward connections 160 according to the invention. In particular, a conventional transceiver 170 can be tuned, on demand, to any channel at 1.2288 MHz within a much larger bandwidth, such as up to 30 MHz. In the case of placement in existing, cell-shared radio frequency bands, these channels are usually made available in the range from 800 to 900 MHz. For wireless systems of the personal communications (PCS) type, the channels are usually allocated in the range from about 1.8 to 2.0 GHz. In addition, there are usually two coherent bands active at the same time, separated by a safety band, such as 80 MHz; and the two coherent bands form a full duplex connection in the forward and reverse direction.

Each of the CDMA transceivers, such as transceiver 140 in subscriber unit 101, and transceivers 172 in base station 170, is capable of being tuned at any given time to a given radio frequency channel. It is generally understood that, for example, a radio frequency carrier of 1.2288 MHz at best provides a total equivalent of continuous transmission with a maximum data rate of about 500 to 600 kbps, within acceptable bit error rate limitations.

In order to make more efficient use of the available bandwidth, however, each radio channel of 1.2288 MHz on the reverse link is divided into a relatively high number of subchannels. In the illustrated example, the bandwidth is divided into 64 subchannels 300, each of which provides a data rate of 8 kbps. A given subchannel 300 is physically implemented by encoding a transmission with one of a number of different pseudo-arbitrary codes and/or code phases that can be assigned. E.g. the 64 subchannels 300 can be defined within a single CDMA radio frequency carrier by using a different coding phase for each defined subchannel 300.

As mentioned above, subchannels 300 are allocated only when necessary. E.g. several subchannels 300 are granted in periods of time where a special ISDN subscriber unit 101 requests that large amounts of data be transmitted. These subchannels 300 are quickly released in periods of time when the subscriber unit 101 is relatively lightly loaded.

The present invention relates in particular to maintaining the reverse connection so that a transmit power level for the subchannels does not need to be restored each time subchannels are removed and then returned.

Fig. 3 is a diagram illustrating how the subchannels are assigned to

the reverse link. It is desirable to use a single radio carrier wave signal on the reverse connection, to the extent possible, to limit power consumption, and to take care of the receiver resources that must be made available in the base station. Therefore, a single channel 350 at 1.2288 MHz is selected from the available radio spectrum.

A relatively high number N, such as 1000 individual subscriber units, is then supported by using a single, long pseudonoise code (pseudonoise, PN) in a special way. First, a number of p phases is selected for the code from among 2<42->1 available different code phases. The p code phase shifts are then used to provide p subchannels. Each of the p subchannels is then further divided into s time slots. Therefore, the maximum number of subscriber units that can be supported is N, p times s. Using the same PN code with different phases and time slots provides many different subchannels, allowing the use of a single rake receiver in the base station 104.

In the above channel allocation system, radio resources are expected to be allocated on an as-needed basis. However, one must also take into account the fact that, in order to set up a new CDMA channel, normally a given reverse link channel must be given time not only to achieve code phase locking, but also to adjust its transmission to the correct power level. The present invention avoids the need to wait for each channel to achieve this each time it is set up by means of several mechanisms described more fully below. In general, the technique is to send a maintenance signal with sufficient frequency for each subchannel, even when in standby mode; i.e. even in the absence of data traffic.

An aim here is to minimize the size of each time slot, which in turn maximizes the number of subscribers that can be maintained in idle mode. The size t of each time slot is determined by the minimum time it takes to guarantee phase locking between the transmitter in the subscriber unit and the receiver in the base station. In particular, a code-correlator in the receiver must receive a maintenance or "heartbeat" signal consisting of at least a certain number of maintenance bits in a certain time unit. As a borderline case, this heartbeat signal is sent by sending at least one bit from each subscriber unit on each reverse link at a predetermined time, e.g. its designated time slot on a predetermined one of the N subchannels.

The minimum time slot duration t therefore depends on a number of factors, including the signal/noise ratio and the expected maximum speed of the subscriber unit in the cell. As for the signal/noise ratio, this depends

where Eb is the energy per bit, No is the ambient noise floor, and lo is the mutual interference from other coded transmissions in the other subchannels on the reverse link that share the same spectrum. Typically, closing the connection requires integration over 8 chip times in the receiver, and 20 times this time is typically required to guarantee detection. Therefore, about 160 chip times are usually required to receive the coded signal correctly on the reverse link. For a code of 1.2288 MHz, Tc, the chip time, is 813.33 ns, so that this

the minimum integration time is around 130^s. This in turn determines the absolute minimum duration for a data bit, and therefore the minimum duration for a slot time, t. The minimum slot time of 130 ^is means that a maximum of 7692 time slots can be made available per second for each phase-coded signal.

Once code phase locking is achieved, the duration of the heartbeat signal is determined by looking at the capture or locking area of the code phase locking circuits in the receiver in the base station. The recipient has e.g. usually a PN code correlator that runs at the code chip rate. An example of such a code correlator uses a delay-lock loop consisting of an early/late detector. A loop filter controls this loop's bandwidth, and this in turn determines how long the code correlator must be allowed to operate before it can guarantee phase locking. This loop time constant determines how much "jitter" Gitter) can be tolerated in the code correlator, such as about 1/8 of a chip time, Tc.

In the preferred embodiment, the system 100 is intended to support so-called nomadic mobility. That is, high mobility functionality in moving vehicles, which is common in cellular telephony, is not expected to be necessary. Rather, the typical laptop user who is active moves only at a brisk walking speed of about 7.2 km/h. At a speed of 7.2 km/h, which corresponds to a speed of 2 m/sec, a user will move 31 meters in 1/8 of the chip time (Tc) 1/1.2288 MHz. It would therefore take about 31 meters divided by 2 meters, or about 15 seconds for such a user to move a distance sufficiently long for him to a point where the code-phase synchronization loop cannot be guaranteed to remain locked. Therefore, as long as a complete synchronization signal is sent on a given reverse link channel every 15 seconds, the reverse link loop will be maintained. In practice, it is preferred not to push this all the way to the limit, and a synchronization heartbeat signal is sent once every number of seconds.

Fig. 4 is a state diagram showing a set of operations performed by the base station 170 and subscriber units 101. The sequence of states entered for the base station 170 is generally illustrated on the left side of the figure, and the sequence of states for the subscriber unit 101 on the right side .

In a first state 400, the subscriber unit 101 is initialized, such as by turning on its battery power. the subscriber unit 101 then sends an initiation message to the base station 170. In this initiation state 402, the subscriber unit performs system determination, pilot channel acquisition, synchronization channel acquisition and other clock control functions, such as e.g. specified through the air interface standard of IS-95B. In reality, the subscriber unit 101 determines the type of system in which it operates, e.g. a dual-mode CDMA, or analog mode, achieves acquisition of the pilot channel by synchronizing its clock control circuits, and also performs a similar clock control function on the sync channel. In addition, an initial open loop reverse power level starting value can be determined, such as by measuring a power level received on a forward link, as is known in the art. If the subscriber unit 101 can perform all of these tasks within a certain specified time period, it can successfully enter a standby mode state 403.

After it is initialized, the subscriber unit 101 can inform the base station 120 of its successful completion of such tasks, by sending an initialization message 430 to the base 170. The base station 120 then enters a state 450, where it assigns a reverse link maintenance channel to the special subscriber 101. This can be done after recognition of the pilot and synchronization, by sending a code phase p and time slot s to be used for this special subscriber unit, in a message. Such a message can e.g. is transmitted on the forward link dialing channel which the subscriber unit continues to monitor during its standby mode state 403.

Also while in the standby state 403, once an open loop power level is established, the subscriber unit 101 periodically enters a state 404 where a heartbeat message is sent to the base station 120 over the reverse link.

Once the base station 170 receives such a heartbeat message, it enters a state 452, where it determines a link quality metric for the reverse link signal received from the subscriber unit 101.

Then, in state 454, this reverse link quality metric is sent as a link quality report (LQR) message over the reverse link to the subscriber unit 101. The LQR message is sent over a dial or sink channel, since no traffic channel is available during standby mode.

LQR can e.g. contains 8 bits of information. The link quality metric can be a bit error rate, a noise energy level expressed as Eb/N0i, or a power level.

Upon receiving the LQR, the subscriber unit enters a state 406, where it calculates its reverse power level, using the received LQR and other information.

The subscriber unit then continues to iterate, through states 404 through 407, to maintain an appropriate power level while in standby mode, until the subscriber unit receives a message indicating that it should enter active mode, or otherwise leave its standby mode -mode.

On the base station side, the states 452, 454 and 456 are similarly repeated for each of the subscriber units which are in the standby mode, while in the idle state.

The heartbeat signal 435 is sent for synchronization message on the assigned maintenance channel at a data rate that need only be fast enough to allow the subscriber unit 101 to maintain synchronization with the base station 170. The heartbeat signal duration is determined by taking into account the capture area of the code-phase-lock circuits and receiver circuits and base station 170.

In a preferred embodiment, the system is intended to support so-called nomadic mobility. That is that one does not expect to encounter operation with relatively high mobility, such as in moving vehicles, which is common for cellular telephony. Rather, the typical laptop user is expected to remain connected only while moving around at a brisk walking speed of around 7 km/h. In this situation, a user will move about 30 meters, and 1/8 of the chip time at 1.2288 MHz. It therefore takes about 30 meters divided by 2 meters, or about 15 seconds for such a user to move a distance long enough to a point where code-phase synchronization cannot be guaranteed. Therefore, as long as a complete heartbeat signal and power control word for a given reverse link channel is exchanged every 15 seconds, the reverse link will remain at the desired power level for a closed loop.

For further information regarding the heartbeat signal arrangement, reference is made to co-existing International Application No. PCT/US99/11607 entitled "Fast Acquisition of Traffic Channels for a Highly Vari-able Data Rate", filed May 26, 1999 and assigned to same copyright holder as this invention.

It can now be understood how the present invention implements power management for closed loop in a code-shared multi-access system which assigns reverse link traffic channels dynamically, also when such traffic channels are not assigned. This is achieved with the base station's deterministic link quality measurement based on a reverse link received signal received in response to maintenance hotstroke signals. The heartbeat signals are sent at a rate that is just fast enough to maintain code phase locking. In response to this, a link quality report message is sent back to the subscriber unit on the forward link, such as on a dial-up or sync channel.

Instead of ISDN, other line and network protocols can be encapsulated, such as xDSL (Digital Subscriber Loop), Ethernet or X.25, and therefore the dynamic allocation plan for wireless subchannels described here can be advantageously used.

Claims (48)

1. A method for use in a base station to provide power control over dynamically assigned return link channels, the method comprising: allocating a return link channel to a code division multiple access (CDMA) user device; dividing the return link channel into multiple subchannels; receiving a message from a CDMA user device over the reverse link channel, the CDMA user device being turned on but not actively transmitting data; determining a link quality metric for the received message, the received message being a maintenance signal for each subchannel at a rate sufficient to maintain code phase locking between the user device and the base station; and sending a power control bit and an allocation on a forward link channel in response to the received message to adaptively control the CDMA user device transmit power level and data rate. 2. Method according to claim 1, where the assigned return connection channel is the only traffic channel allocated to the CDMA user device. 3. Method according to claim 1, where the transmission rate of the message received from the CDMA user device depends on the CDMA user device's maximum expected physical movement speed. 4. Method according to claim 1, wherein the link quality metric indicates a bit error measurement. 5. Method according to claim 1, where the link quality metric indicates a noise level measurement. 6. Method according to claim 1, wherein the link quality metric indicates a signal power level measurement. 7. Method according to claim 1, wherein the power control bit is sent on a forward connection call channel. 8. Method according to claim 1, where the power control bit is sent on a synchronization channel. 9. Method according to claim 1, where the power control bit is sent on a pilot channel. 10. Method according to claim 1, where the power control bit controls the CDMA user device's transmission power level over the return data channel. 11. Method according to claim 1, where the base station sends and receives digital signals over at least one radio frequency channel using radio signals. 12. Method according to claim 12, where each radio frequency channel comprises a plurality of sub-channels where a plurality of different codes are assigned to each sub-channel. 13. Code division multiple access (CDMA) base station comprising: an antenna; a controller configured to allocate a return link channel to a code division multiple access (CDMA) user device, wherein the return link channel is divided into several subchannels; a CDMA transceiver configured to receive a message from the CDMA user device over the return link channel, the CDMA user device being turned on but not actively transmitting data; wherein the controller is further configured to determine link quality metrics for the received message, the received message being a maintenance signal for each subchannel received on the return link channel at a rate sufficient to maintain code phase locking between the user device and the base station; while the CDMA transceiver is further configured to transmit a power control bit and an allocation on a forward link channel in response to the received message to adaptively control and maintain the CDMA user equipment transmit power level and data rate. 14. Base station according to claim 13, where the assigned return connection channel is the only traffic channel allocated to the CDMA user device. 15. Base station according to claim 13, where the transmission rate of the message received from the CDMA user device depends on the CDMA user device's maximum expected physical movement speed. 16. Base station according to claim 13, wherein the link quality metric indicates a bit error measurement. 17. Base station according to claim 13, where the link quality metric indicates a noise level measurement. 18. Base station according to claim 13, wherein the link quality metric indicates a signal power level measurement. 19. Base station according to claim 13, wherein the power control bit is sent on a forward link calling channel. 20. Base station according to claim 13, where the power control bit is sent on a synchronization channel. 21. Base station according to claim 13, where the power control bit is sent on a pilot channel. 22. Base station according to claim 13, where the power control bit controls the CDMA user device's transmission power level over the return data channel. 23. Base station according to claim 13, where the base station sends and receives digital signals over at least one radio frequency channel using radio signals. 24. Base station according to claim 23, where each radio frequency channel comprises a plurality of sub-channels where a plurality of different codes are assigned to each sub-channel. 25. Code division multiple access (CDMA) user device comprising: an antenna; and a CDMA transceiver configured to receive a message from a base station allocating a subchannel for a reverse link channel allocated by the base station for use by the user device; the CDMA transceiver being configured to send a maintenance signal to the base station over the assigned subchannel of the return link channel at the time the CDMA user equipment is turned on but not actively transmitting data; the CDMA transceiver being further configured to receive a power control bit and an assignment on a forward link channel from the base station in response to the transmitted maintenance signal and based on a link quality metric for the maintenance signal, the power control bit for each subchannel being received at a rate sufficient to maintain code phase - locking between the user device and the base station; and a controller configured to adaptively control and maintain the transmit power level and data rate of the CDMA user device using the received power control bit and allocation. 26. CDMA user device according to claim 25, wherein the allocated return connection channel is the only data channel allocated to the CDMA user device. 27. CDMA user device according to claim 25, where the transmission rate of the message sent to the base station depends on the maximum expected rate of physical movement for the CDMA user device. 28. CDMA user device according to claim 25, wherein the power control bit is received on a forward link calling channel. 29. CDMA user device according to claim 25, wherein the power control bit is received on a pilot channel. 30. CDMA user device according to claim 25, wherein the power control bit controls the CDMA user device's transmission power level over the return data channel. 31. The CDMA user device of claim 25, wherein the link quality metric indicates a bit error measurement. 32. CDMA user device according to claim 25, wherein the link quality metric indicates a noise level measurement. 33. CDMA user device according to claim 25, wherein the power control bit is received on a synchronization channel. 34. The CDMA user device of claim 25, wherein the link quality metric indicates a signal power level measurement. 35. CDMA user device according to claim 25, where the user device sends and receives digital signals over at least one radio frequency channel using radio signals. 36. CDMA user device according to claim 35, where each radio frequency channel comprises a plurality of sub-channels where a plurality of different codes are assigned to each sub-channel. 37. Method for use in a code division multiple access (CDMA) user device, to provide power control over dynamically assigned return link channels, the method comprising: receiving a message from a base station assigning a subchannel for a return link channel allocated by the base station for use by the user device; sending a maintenance signal to the base station over the assigned subchannel of the reverse link channel at the time the CDMA user equipment is turned on but not actively transmitting data; receiving a power control bit and an assignment on a forward link channel from the base station in response to the sent maintenance signal and based on a link quality metric for the maintenance signal, the power control bit for each subchannel being received at a rate sufficient to maintain code phase locking between the user device and the base station; and adaptively controlling and maintaining the CDMA user device transmit power level and data rate using the received power control bit and allocation. 38. Method according to claim 37, wherein the allocated return connection channel is the only data channel allocated to the CDMA user device. 39. Method according to claim 37, wherein the transmission rate of the message sent to the base station depends on the maximum expected rate of physical movement for the CDMA user device. 40. The method of claim 37, wherein the link quality metric indicates a bit error measurement. 41. Method according to claim 37, wherein the link quality metric indicates a noise level measurement. 42. The method of claim 37, wherein the link quality metric indicates a signal power level measurement. 43. Method according to claim 37, wherein the power control bit is received on a forward connection call channel. 44. Method according to claim 37, where the power control bit is received on a synchronization channel. 45. Method according to claim 37, where the power control bit is received on a pilot channel. 46. Method according to claim 37, wherein the power control bit controls the CDMA user device's transmission power level over the return data channel. 47. Method according to claim 37, where the CDMA user device sends and receives digital signals over at least one radio frequency channel by means of radio signals. 48. Method according to claim 37, where each radio frequency channel comprises a plurality of sub-channels where a plurality of different codes are assigned to each sub-channel.